The OpenConnect VPN Protocol Version 1.2
draft-mavrogiannopoulos-openconnect-03
Network Working Group N. Mavrogiannopoulos
Internet-Draft Red Hat
Intended status: Informational October 2, 2020
Expires: April 5, 2021
The OpenConnect VPN Protocol Version 1.2
draft-mavrogiannopoulos-openconnect-03
Abstract
This document specifies version 1.2 of the OpenConnect Virtual
Private Network (VPN) protocol, a secure VPN protocol that provides
communications privacy over the Internet. That protocol is believed
to be compatible with CISCO's AnyConnect VPN protocol. The protocol
allows the establishment of VPN tunnels in a way that is designed to
prevent eavesdropping, tampering, or message forgery.
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This Internet-Draft will expire on April 5, 2021.
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Internet-Draft The OpenConnect Version 1.2 October 2020
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Terminology . . . . . . . . . . . . . . . . 3
1.2. Goals of This Document . . . . . . . . . . . . . . . . . 3
2. The OpenConnect Protocol . . . . . . . . . . . . . . . . . . 3
2.1. VPN Session Establishment . . . . . . . . . . . . . . . . 3
2.1.1. Server Authentication . . . . . . . . . . . . . . . . 3
2.1.2. Client Authentication . . . . . . . . . . . . . . . . 4
2.1.3. Exchange of Session Parameters . . . . . . . . . . . 9
2.1.4. Establishment of Primary TCP Channel (CSTP) . . . . . 11
2.1.5. Establishment of Secondary UDP Channel (DTLS) . . . . 11
2.2. The CSTP Channel Protocol . . . . . . . . . . . . . . . . 12
2.3. The DTLS Channel Protocol . . . . . . . . . . . . . . . . 13
2.4. The Channel Re-Key Protocol . . . . . . . . . . . . . . . 13
2.5. The Keepalive and Dead Peer Detection Protocols . . . . . 14
3. Security Considerations . . . . . . . . . . . . . . . . . . . 15
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
5. Normative References . . . . . . . . . . . . . . . . . . . . 16
Appendix A. Name for Application-Layer Protocol Negotiation . . 19
Appendix B. Compression . . . . . . . . . . . . . . . . . . . . 19
Appendix C. DTD declarations . . . . . . . . . . . . . . . . . . 19
C.1. config-auth.dtd . . . . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
The purpose of this document is to specify the OpenConnect VPN
protocol in a detail in order to allow for multiple interoperable
implementations. This is the protocol used by the OpenConnect client
and server [OPENCONNECT-CLIENT][OPENCONNECT-SERVER], and is believed
to be compatible with CISCO's AnyConnect protocol.
This protocol's design follows a minimalistic modular philosophy. It
delegates several protocol-related elements often considered as core
VPN features and diversifiers, to standards protocols. That
delegation, allows a minimalistic core protocol which contains very
few security related elements and is decoupled from cryptography.
That in turn transfers the auditing requirements due to cryptographic
and negotiation protocols to dedicated for that purpose components.
In particular the Openconnect VPN protocol uses standard protocols
such as HTTP, TLS [RFC8446] and DTLS [RFC6347] to provide a VPN with
data security and authenticity.
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